Proper piping system & appropriate diameters for sanitary?

Hello everyone,

for our old building project, I want to completely reinstall all (pipe) lines.
However, I already have 2 questions in advance:

- for aluminum composite pipes, which system is better: crimping or screwing?
- which diameters are generally used for radiators and domestic hot water?

The layout will be:
Basement: heating system in the basement, there only 1 cold water outlet (washing machine separately, with rainwater supply)
Ground floor: kitchen with 1 sink (hot + cold) + dishwasher,
bathroom with shower + washbasin (toilet separately, with rainwater supply),
5 radiators for 5 rooms, total 90m²
Attic: bathroom with shower + washbasin (toilet separately, with rainwater supply),
4 radiators for 4 rooms, total 65m²

Hello,

unfortunately, it is not that simple. To determine the pipes for the heating, you need to know how much heating demand you have; accordingly, the pipe diameter is chosen.

With water, it is easier. Riser pipe 32 mm plastic pipe or 28 mm stainless steel pipe. Supply line 20 mm plastic pipe inside the bathroom then 16 mm. It is best to lay a ring so that you can easily see the pipe diameter.

Regarding processing. I use Rehau, which has sliding sleeves; the advantage of this pipe is that the connectors do not reduce the pipe diameter. Alternatively, I also use Geberit Mepla and Mapress as well as Sanipex (screw connectors). You just have to know that for press and sliding sleeve connections, you need special machines.

Alternatively, push-fit systems such as Geberit Pushfit require no special tools (except the calibrator).

To determine the pipes for the heating system, you need to know how much heating demand you have; accordingly, the pipe cross-section is chosen.

Can a layperson do that or are there standard values? Alternatively: an on-site appointment with an energy consultant for KFW assessment is still pending, presumably they should be able to estimate that as well.

With water it’s easier. Riser 32 mm plastic pipe or 28 mm stainless steel pipe. Supply line 20 mm plastic pipe inside the bathroom then 16 mm.

The terms are new to me but I assume:
- Riser = main pipe from the basement up to the floors
- Supply line = per room (i.e., one 20 mm for the kitchen, one 20 mm for each bathroom)
- 16 mm for each connection

I once read that thinner diameters are recommended for hot water (consistently 16 mm) so that hot water arrives faster. That probably only works if no water is drawn simultaneously elsewhere, like at the sink while someone is showering, right?

It's best to lay a loop so you can comfortably determine the pipe cross-section.

Okay, that’s something to consider. About 10 years ago I was involved in the interior finishing of a prefab house and I remember that the water supply per floor was arranged like this: supply line to the shower -> to the sink -> possibly to the kitchen faucet. All the same cross-section (no idea which), no loop system, no circulation pump.

Regarding the workmanship.....

I was more thinking about whether both systems are 100% safe and mature or if one is more suitable for long-term reliability. I guess that the screw systems are mainly designed so they can be undone again at some point, whereas the press systems are primarily intended for permanent / concealed / under screed installations.

You just have to know that for press and sliding sleeve connections you need special machines.

Yes, I’ve seen that, although there are also hand-pressing pliers.

Work on drinking water pipes belongs in the hands of a sanitary installer and not a social pedagogue. Apart from the fact that you are not allowed to perform the work, you have a serious problem in case of damage since no insurance applies here. Your obvious ignorance on the subject only underscores this...

That sounds harsh, but unfortunately must be said. Screwing on faucets yourself or installing a sink is more suitable for DIY.

Work on drinking water pipes belongs in the hands of a plumber and not those of a social pedagogue.[...]Your obvious ignorance on the subject only underscores this....

Thank you for this helpful contribution to my question.
And that is exactly why I am here - to fill this knowledge gap.
Would you like to contribute?

As I said, you are not allowed to do that and no one can help you there either.

If a plumber comes to you tomorrow and says he wants to teach a 10th grade class in German and history starting next week and quickly needs the material that is currently being taught to them and how to convey it - what do you say to him?